For me it was the Cell with Jennifer Lopez. It was about her getting inside a serial killer/rapist's mind.

Ironically, I just watched this movie last night for the first time since it original released. It was much better back in the late 90's then it was watching it again here in 2013. Not "scary" or "disturbing" at all.

How about Exorcist? Yeah, I realize this isn't the entire consensus, but many others would agree. Not you younger ISH generation, but just speaking in general terms.

More recently, Human Centipede and even more disturbing Human Centipede 2.